Between 1874 and 1881, approximately forty county atlases were published in Canada, covering counties in the Maritimes, Ontario and Quebec. Thirty-two of these atlases were produced for Ontario by the following five companies: H. Belden & Co. (17); H.R. Page & Co. (8); Walker & Miles (5); J.H. Meacham & Co. (1); H. Parsell (1). Two types of county atlases exist for Ontario, those that covered a single county or multiple adjacent counties, and those that were published as supplements to Dominion of Canada atlases. In total, 40 Ontario counties were covered by these 32 atlases. The Division holds most of the atlases and they have formed the basis for: In Search of Your Canadian Past: The Canadian County Atlas Project.
Records for the holdings are in the McGill Library on-line catalogue.